This is a long-term project to study the epidemiologic characteristics of congenital malformations in singletons and twins; to assess and interpret the influence of maternal, socioeconomic, neonatal, medical and other environmental factors on the occurrence of congenital malformations; to determine the risk of familial occurrence and to elucidate the role of genetic factors and the mode of inheritance of certain malformations; to determine the severity and clinical significance of congenital malformations and their associations with neurological, physiological and sensory handicaps; and to assess the long-range effects of malformations on survival, growth and development. BIBLIOGRAPHIC REFERENCES: Patil, S.R., Lubs, H.A., Kimberling, W.J., Brown, J., Cohen, M., Gerald, P., Hecht, F., Moorehead, P., Myrianthopoulos, N. and Summitt, R.L.: Chromosomal abnormalities ascertained in a collaborative survey of 4,342 seven and eight year old children: frequency, phenotype and epidemiology. In E.B. Hook and I.H. Porter (Eds.): Population Cytogenetics. New York, Academic Press, 1977, pp. 103-132. Lubs, H.A., Patil, S.R., Kimberling, W.J., Brown, J., Cohen, M., Gerald, P., Hecht, F., Myrianthopoulos, N. and Summitt, R.L.: Q and C banding polymorphisms in seven and eight year old children: racial differences and clinical significance. In E.B. Hook and I.H. Porter (Eds.): Population Cytogenetics. New York, Academic Press, 1977, pp. 133-160.